The present invention relates to a motor retractor system, in which when pulling out a seat belt, a winding device motor does not wind the belt, and when an occupant releases the seat belt restraint, the motor winds the seat belt.
In a conventional retractor equipped in an automobile, a seat belt or webbing is pulled out with a through-tongue from a spool of a winding device or retractor fitted in the automobile, and the through-tongue engages a buckle. An occupant is restrained in a seat by tension in the winding direction of the seat belt pulled out from the spool.
However, because of constant contact of the seat belt with a body, if the tension is too large, the occupant might feel discomfort by the large oppressing force. On the other hand, if the tension is too small, the retracting force is insufficient to wind the seat belt smoothly.
Also, in a conventional retractor, since a single return spring is built therein, an urging force of the return spring increases with pulling out the seat belt, resulting in an enlarged retracting force.
As means for solving the problem associated with the single return spring, a tension-reducer mechanism comprising two truncated cone-shaped rope pulleys with spiral guide grooves has been developed (disclosed in Japanese Patent No. 2711428).
In addition to securely restraining and protecting an occupant upon an emergency, a seat belt winding device for an occupant restraint and protection system has been also developed (disclosed in Japanese Patent Publication No. 9-132113), in which an electric motor controls the seat belt tension by detecting a distance to other vehicles in front and behind during moving, and comfort performance of wearing the belt under a normal condition is improved.
However, for the most of the seat-belt retractors using a motor, the motor control is needed to monitor the seat belt pulled out by an occupant, the position of the seat belt, tension of the seat belt, and the amount of a spool rotation, via various sensors and encoders. Further, when an electrical signal or an electrical power is lost, auxiliary means is needed to operate the seat belt restraining, and a direct spring force can spoil the comfort performance.
In order to solve the problems described above, it is an object of the present invention to provide a motor retractor system capable of restraining an occupant in a seat with a comparatively small force without excessive pressing, and quickly storing the seat belt into a winding device or retractor upon releasing the seat belt, while easy pull-out of the seat belt can be comfortably performed.
Further objects and advantages of the invention will be apparent from the following description of the invention.
In order to achieve the above-mentioned objects, a motor retractor system according to the first aspect of the invention comprises a first winding device having a motor for driving a shoulder belt in the winding direction, and a second winding device having a tension-applying device for applying a constant tension in the winding direction to a lap belt extending from the shoulder belt through a through-tongue. A control unit controls the motor to drive when the through-tongue coupled to a buckle is released from the buckle. Therefore, the shoulder belt can be smoothly pulled out, and when the through-tongue is buckled up, an occupant can be restrained by the seat belt with a comfortable force and no slack. When the through-tongue is released from the buckle, the seat belt can be promptly withdrawn to the first winding device.
In a motor retractor system according to the second aspect of the invention, the control unit may drive the motor in the first winding device in the winding direction when the through-tongue is released from the buckle. Therefore, the first winding device can wind the seat belt promptly.
A motor retractor system according to the third aspect may further comprise belt-storage detecting means disposed in the first winding device and the second winding device for detecting a state of the shoulder belt or the lap belt. Therefore, the seat belt length wound in the first winding device and pulled out of the second winding device can be precisely monitored and controlled.
In a motor retractor system according to the fourth aspect of the invention, when an occupant is wearing the shoulder belt and the lap belt, only the second winding device creates a winding force, and the first winding device does not drive. Therefore, the occupant can be comfortably restrained in the seat due to a small force of the second winding device.
In a motor retractor system according to the fifth aspect of the invention, when the detecting means confirms that the belt is wound up to a predetermined point, the first winding device may stop winding the shoulder belt. Therefore, the seat belt can be pulled out again.